Explosion kills one, injures 30 in Syria

This photo released by the official Syrian news agency SANA shows rescue teams investigating the scene after an explosion Sunday near a government security building in Aleppo, Syria.

BEIRUT — An explosion struck near a Syrian government security building in the northern city of Aleppo Sunday, while a harsh security crackdown prevented opposition rallies marking one year since the first nationwide protests of the uprising against President Bashar Assad.

The Syrian state news agency called the Aleppo explosion a "terrorist bombing" and said one policeman and one civilian were killed, while 30 were injured. It was the second attack in two days on regime strongholds.

Three suicide bombings in Damascus on Saturday killed 27 people. Two of them also targeted government security buildings and the opposition, which it claims is made up of "terrorist" groups carrying out a foreign conspiracy.

Aleppo and Damascus, Syria's two largest cities, have been struck by a number of suicide bombings since December. Both are critical centers of support for Assad and have remained insulated from the unrest shaking the country for the past year. No one has claimed responsibility for any of the weekend attacks.

The string of large-scale bombings near government security buildings in Damascus and Aleppo have added a mysterious element to the anti-government revolt. After other similar attacks, U.S. officials suggested al-Qaida militants may be joining the fray.

A previously unknown Islamist group calling itself Al-Nusra Front to Protect the Levant claimed responsibility for previous attacks in a video posted online, saying it carried them out "to avenge the people of Homs." Homs is an opposition stronghold in central Syria that has been hard hit in the government crackdown.

Al-Qaida's involvement could further fuel the sectarian tensions that the uprising has already stoked. Al-Qaida's supporters are largely Sunni Muslim extremists. Syria's military and political leadership is stacked with members of the minority Alawite sect, an offshoot of Shiite Islam to which Assad and the ruling elite belong. The Alawite leaders of Syria are closely allied with Shiite Iran.

Sunnis are the majority in the country of 22 million and make up the backbone of the opposition.

Many activists consider March 18, 2011, the start of the anti-Assad uprising. Thousands took to the streets in cities across Syria on that day, and security forces killed marchers in the southern city of Daraa.

Since then, Assad's security forces have sought to crush all signs of dissent, and protest and international condemnation have spread. Many in the opposition have taken up arms to defend themselves and attack government forces as the increasingly militarized conflict has become one of the bloodiest of the Arab Spring.